Re: [PATCH] staging: comedi: remove __user annotation inside of struct's

Dan Carpenter
2012-05-09T10:28:05Z

On Wed, May 09, 2012 at 11:20:07AM +0100, Ian Abbott wrote:
> On 2012-05-09 00:55, H Hartley Sweeten wrote:
> >On Tuesday, May 08, 2012 4:41 PM, H Hartley Sweeten wrote:
> >>
> >>The structs' comedi_insn, coomedi_insnlist, comedi_cmd,
> >>comedi_chaninfo, and comedi_rangeinfo are all passed to
> >>the kernel from user space using ioctl commands. They
> >>are then copied to kernel space using copy_from_user()
> >>before the data is passed to the drivers.
> >>
> >>The __user annotation should not be used with variables
> >>inside the struct. This produces a lot of sparse warnings
> >>like:
> >>
> >>warning: dereference of noderef expression
> >>
> >>Signed-off-by: H Hartley Sweeten<hsweeten@visionengravers.com>
> >>Cc: Ian Abbott<abbotti@mev.co.uk>
> >>Cc: Mori Hess<fmhess@users.sourceforge.net>
> >>Cc: Greg Kroah-Hartman<gregkh@linuxfoundation.org>
> >>
> >>---
> >>
> >>Note: This patch exposes some new warnings about different
> >>address space. These will be addressed.
> >
> >Please ignore this patch.
> >
> >It appears the annotations in the struct definitions are correct.
>
> Personally, I think you were on the mark with the patch. It's
> better to avoid using __user in comedi.h so it can be used as-is in
> user-space.

Sparse is useful so we shouldn't break it. I always run sparse over
my patches before submission and look at the warnings. Except if
they scroll off the page. In that case, I just figure that the
author deserves the bugs.

We could just do some ifdeferry to fix it for userspace.

regards,
dan carpenter